1. Field of the Invention
The present invention is generally related to an air induction system of a marine engine and, more particularly, to a sound attenuating structural assembly for reducing the noise emanating from the region of an idle air control valve.
2. Description of the Prior Art
Many different types of internal combustion engines comprise an idle air control valve (IACV) for the purpose of regulating the flow of air into an intake manifold of an engine when the throttle plate within a throttle body is either closed or nearly closed.
U.S. Pat. No. 5,722,367, which issued to Izydorek et al on Mar. 3, 1998, describes an engine idle speed air control system. A control device for bypassing intake air around a closed throttle valve of an operating engine while it is idling is described. The device has a main flow control valve controlling bypass air flow and the bypass air passageway of the device which is moveable to closed and open positions by a diaphragm actuated by an engine intake vacuum controlled by a pilot valve actuated by a solenoid. The main valve, pilot valve and plunger of the solenoid are all movably received on and supported by a stationary slide rod which preferably extends into the coil of the solenoid and is supported adjacent only one end in a cantilever fashion. The main valve includes a main valve body with piston head movable with a flow clearance in and out of an air passage bore of the air outlet side of the bypass air passageway. An annular main valve seat is located at the open upstream of the bore through which the piston head moves in its axial travel between fully open and close positions of the main valve. The main valve also includes a flexible valve disc upstream of the valve body which is engageable with the main valve seat to fully close the same. The valve disc is controllably peeled off the main valve seat by a wedge shaped face of the piston head during initial opening travel of the main valve. The piston is also peripherally shaped to cooperate with the air passage bore and main valve seat to controllably vary the flow controlling cross sectional area of the bypass passageway and hence the bypass air flow rate as a function of incremental axial travel of the main valve along the slide rod.
U.S. Pat. No. 4,337,742, which issued to Carlson et al on Jul. 6, 1982, describes an idle air control apparatus for an internal combustion engine. The apparatus for a vehicle driving internal combustion engine has an air induction passage and includes a control valve in the air induction passage controlled by a stepper motor in response to the arithmetic count of applied electrical pulses. A register is used to store a valve control number representing the currently desired position of the control valve. Upon occurrence of a predetermined engine loading event, the system changes the valve control number in response thereto. An up-down counter is effective to arithmetically count the pulses applied to the stepper motor and thus indicate actual control valve position. A closed loop control is effective to compare the contents of the up-down counter and register and apply pulses to the stepper motor at the first predetermined rate to reduce any difference therebetween. A speed trim loop active only during occurrence of the predetermined steady state idle condition is used to compare actual engine speed with the desired engine idle speed and arithmetically change the valve control number in the register at a second predetermined rate substantially lower than the first predetermined rate to reduce any difference between the speeds. Therefore, idle air control responds to large, sudden engine load changes and environmental factors to prevent engine stall, but ignores small random speed fluctuations to maintain a stable engine idle.
The patents described above are hereby expressly incorporated by reference in the description of the present invention.
Various types of idle air control systems known to those skilled in the art will be described below in conjunction with FIGS. 1-4. Because of the sound that emanates from the region of an idle air control valve, it would be significantly beneficial if an inexpensive method could be provided for reducing the sound level caused both by the operation of the idle air control valve and the air flowing through the conduit associated with the idle air control system.
An idle air intake system for a marine engine, made in accordance with the preferred embodiment of the present invention, comprises a throttle body structure and a throttle plate rotatably supported within the throttle body structure. The throttle plate is rotatable in order to regulate a flow of air through the throttle body structure from a first region on a first side of the throttle plate to a second region on a second side of the throttle plate. An air conduit is provided with an inlet and an outlet, with the outlet being disposed in fluid communication with the second region, on the second side of the throttle plate, and the inlet being disposed in fluid communication with a location which is at a pressure generally equal to the pressure within the first region, on the first side of the throttle plate. The present invention further comprises a valve that is connected in fluid communication with the air conduit for controlling the rate of air flow from the inlet to the outlet. It also comprises a fibrous pad disposed within the air conduit proximate the inlet.
The fibrous pad can comprise a plurality of polyester fibers. The inlet of the air conduit can be disposed within a wall of the throttle body structure at a location above the throttle plate.